A nitride semiconductor has characteristics such as high saturation electron velocity and a wide band gap. Accordingly, various studies are being made on the application of a nitride semiconductor to a high withstand voltage and high output semiconductor device utilizing the characteristics. For example, GaN-based high electron mobility transistors (HEMT) have recently been used as power devices.
Some GaN-based HEMT includes a gate electrode having what is called a T-shaped structure. This GaN-based HEMT can have a reduced gate resistance while having a shortened gate length.
In a conventional GaN-based HEMT including the T-shaped gate electrode, however, an electric field is likely to concentrate near a drain electrode side end portion of an eaves-shaped portion as described also in Patent Document 2. An art to alleviate such electric field concentration is described in Patent Document 2, but this art has a problem of difficulty in obtaining excellent high-frequency characteristics even though capable of attaining the end desired.
Patent Document 1: Japanese Laid-open Patent Publication No. 2014-229879
Patent Document 2: Japanese Laid-Open Patent Publication No. 2015-12037